relax certification revocation regulations

[depressiveRobot]

Revision of the scs-0004 standard based on discussions in the SIG Standardization/Certification:

• https://github.com/SovereignCloudStack/minutes/blob/main/sig-standardization/20250626.md#certification-revocation-if-testschecks-fail
• https://github.com/SovereignCloudStack/minutes/blob/main/sig-standardization/20250710.md#finalize-discussions-on-scs-0004-certification-revocation

This PR attempts to implement this as follows:

• Relaxes the regulations regarding test suite reliability and frequency as they are currently not part of the SCS-compatible certification. It will be part of an SCS-sovereign certification in the future.
• Changes wording "nightly" to "daily" because it is not night everywhere at the same time.
• Make it clearer that the operator is responsible for successfully passing tests and checks.
• The supplement has been revised so that only “regularly” is used instead of specific time periods (which are defined by the standard). That way the supplement remains up to date even if the timings are adjusted in the standard.